phys2bids 3.0

[smoia]

We've been working for a while on phys2bids v2, but it might be time to move further and get a breaking improvement.
For instance, we could simplify and adjust the system call, and refactor some points in the code to get a better workflow, without being worried of backward compatibility.

I opened a project to keep track of the changes we want to see implemented, but there's still plenty of room to decide what features we want to add before we get to v3!

Don't be afraid of discussing it here, or open new issues as necessary.

Outstanding questions

- What features do you expect from phys2bids 3.0?